Barely contain one's anger (6)
I believe the answer is:
seethe
'barely contain one's anger' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for seethe that I've seen before include "Bubble gently like boiling water" , "Barely contain one's anger" , "Be furious" , "Be silently angry" , "(Of liquid) move as if boiling" .)